Electroluminescent devices have provided illumination to a variety of products including display panels, board games, watch faces, and keyboards. Electroluminescent devices typically include a layer of phosphor-containing material disposed between two electrodes, at least one of the electrodes being light-transmissive.
Electroluminescent devices may be manufactured as discrete cells or as large panels, and may be formed on rigid or flexible substrates. Each component of the device may be formed as a separate layer, such as a foil sheet serving as an electrode, and a planar dielectric sheet, with the layers being laminated together via a heat and pressure process. Alternatively, the layers may be combined into overlapping coatings printed on a substrate, as is the case for a layer of light-transmissive conductive ink serving as a top electrode followed by a layer of phosphor ink in a dielectric matrix and then another conductive ink coating serving as a back electrode. Electroluminescent devices have found widespread uses, e.g. in signs, watch faces, and as back lighting for keyboards.
Electroluminescence technology has become increasingly important to enable homogeneous luminous surfaces free of shadow. Power consumption and structural thickness (of the order of magnitude of a millimeter or less) are desirably low. Typical uses include, apart from the background illumination of liquid crystal displays, the back-lighting of transparent films that are provided with lettering and/or image motifs. Thus, transparent electroluminescent arrangements, for example electroluminescent luminous boards based on glass or transparent plastics, which can serve for example as information carriers, advertising panels, or for decorative purposes, are known from the prior art.